Knock-out



1934. H. A. CALDERWOOD 1,944,706 I KNOCK-OUT Filed April 24, 1931INVENTOR BY His ATTORNEYS Patented Jan. 23, 1934 UNITE STATES PATENTOFFICE- KN OCR-OUT Application April 24, 1931. Serial No. 532,409

1 Claim.

This invention relates to electrical apparatus. More specifically theinvention relates to protective means for such apparatus and from astill more specific viewpoint, the invention relates to i so-calledpryouts or knock-outs.

Among other objects the invention has for its purposes to providearrangements in which the knock-outs may be readily and quickly removedif and when desired and which are, nevertheless,

" held securely in their protective positions up to the time that theyare removed.

Other objects and advantages will appear as the invention is hereinafterdisclosed.

Referring to the drawing which illustrates 15 what I now considerpreferred physical embodi ments of the invention:

Fig. 1 is an elevational view of a knock-out box embodying one form ofmy invention.

Figs. 2, 3 and 4 are fragmentary detail elevations illustrating modifiedforms of the invention.

Fig. 5 is a fragmentary detail perspective view showing how a knock-outof the type shown in Fig. 1 may be removed.

Referring to the drawing, the box wall, 10, con- 2 structed of suitablemetal or other protective material, is shown provided with a pluralityof knock-outs 11' formed by punching out the greater part or theperiphery as indicated at 12; the punching being preferably through theentire thickness of the wall of the box. Each of the knock-outs 11 isshown provided with an intact portion 13 which connects it integrallywith the wall of the box preferably in the plane of the wall 10 untilthe knock-out is removed.

36 For the purpose of removing the knock-out, the wall 10 of the casingor box is shown provided in Fig. 1, with a cut away portion or slot 14,in this instance shown wholly outside the area of the adjacent knock-outbut communicating withthe ll; opening left by the knock-out after it hasbeen removed.

when it is desired to remove the knock-out of the type shown in Fig. 1.a screw driver or similar tool is inserted into the corresponding slot14 I; as shown in Fig. 5 and then operated as a lever about the loweredge of the slot 14 asa fulcrum so as to pry the knock-out 11 outwardlywith respect to the plane of the box or casing wall 10 so that theintact portion 13 is, or may be,

50, readily ruptured. Depending upon the nature of the material of whichthe wall 10, knock-out 11 and intact portion are constructed, the intactportion 13 may be ruptured merely by thev prying out operation justdescribed or, if the intact portion is more resistant it may benecessary to bend the pried-out disk 11 back and forth one or moretimes. with respect to the wall of the box 10 so as to rupture theintact portion.

After any knock-out has been removed the opening that is left may beemployed in the usual manner to receive a rigid or flexible conduit forelectrical wires or conductors, or other device or appliance.

The invention is susceptible to modification. Thus, in Fig. 2, the slot114 for receiving the screw driver or other removing tool, is not, as inthe case of Fig. 1, wholly in the walllO of the box or casing but lies,in part, within the boundary of the knock-out or pry-out 11. In the formV shown in Fig. 2 the tool-receiving slot 114 lies partially outside ofthe periphery of the disk 11 (i. e. partially in the box wall 10), andpartially within or. inside the periphery of the disk 11 (i. e. withinthe boundary of the pry-out). The construction and operation of the formof inven- I tion shown in Fig. 2 will be clear in view of the foregoingdescription of Fig. 1 supplemented by the description of Fig. 2 justmade.

In Fig. 3 the construction and operation are thesame asin the caseofFig. 1 and Fig. 2 except for the following difierences. In this case(Fig. 3), the slot 214 which is adapted to re-. ceive the bit or bladeof the screw driver or other removing tool is so disposed as to besubstantially radial with respect to the disk 11 but otherwise it issimilar to the form shown in Fig. 2 in that it overlaps the boundary orperiphery of the disk 11. In this case (Fig. 3) in order to remove theknock-out, the screw driver blade, after insertion into the slot 214,engages the lower end of the slot 214 as a fulcrum with the lower edgeof the screw driver blade in contact with thisfulcrum" and the upperedge of the screw driver blade is employed to engagethe knock-out andpry it outwardly. In certain cases this construction is Q especiallyadvantageous in that the blade of the screw driver or other removingtool is less likely to be bent or deformed in the knock-out removingoperation.

Still another modification is illustrated in Fig. 4, which shows aconstruction otherwise similar to those shown in Figs. 1, 2 and 3,except that in Fig. 4 the slot 314 for receiving the bit or blade of thescrew driver or other removing tool, is located wholly within theboundary or periphery 1 of the disk or knock-out 11. The operation inremoving this knock-out is quite similar to that set forth above'inconnection with Fig. l and needs no further description.

It will be understood. of course, that the varithe best embodimentsthereof, but I desire to have it understood that the apparatus disclosedis only illustrative and that the invention can be carried out by othermeans. Also, while it is designed to use the various features andelements in the combinations and relations described, some of these maybe altered and others omitted and some of the features of eachm0dification may be embodied in the others without interfering with themore" general results outlined, and the invention extends to such usewithin the scope of the appended claim.

What I claim is:

In an electric protective means, a casing having a pry-out in a wallthereof, said pry-out being provided with an opening for the receptionof a prying'tool whereby said pry-out may be pried loose from said wall,said pry-out being defined by a portion of the circumference-of acircle, said opening being disposed partly within and partly withoutsaid circle, said opening being elongated and having its long dimensionlying substantially radially with respect to said circle.

- HUGH A. CALDERWOO Edit)

